WebVOWL is a popular Ontology Visualization tool used by researchers and practitioners as a standalone tool or embedded in larger data integration tools. Unfortunately, its performance, especially when visualizing large ontologies, leaves much to be desired. Here, we demonstrate a new version of WebVOWL optimized for speed. We describe our analyses of the original tool’s run-time complexity and how we reduced the theoretical complexity and practical run-time by orders of magnitude. In the demonstration, we will show the side-by-side performance monitored behavior of the original WebVOWL with our version on tasks such as visualizing a large ontology, filtering, and collapsing sub-graphs.